Machines for compression molding closure shells, or compression molding sealing liners within closure shells, typically include a turret or carousel that rotates around a vertical axis. A plurality of molds are provided around the periphery of the carousel, in the form of male and female mold sections that are aligned along vertical axes parallel to the axis of rotation. Cams drive one or both of the mold sections of each pair between an open position, in which a molded part is stripped from the male mold section and a charge of plastic material is placed in the female mold section, and a closed position in which the male and female mold sections are brought together to compression mold the shell or liner. In a liner machine, premade shells are placed in a nest when the mold sections are open, and a charge or pellet of liner material is placed within the shell before the molds are closed. U.S. Patents that illustrate machines of this type for compression molding plastic closure shells include U.S. Pat. Nos. 5,670,100, 5,989,007, 6,074,583 and 6,478,568. U.S. Patents that illustrate machines of this type for compression molding sealing liners within closure shells include U.S. Pat. No. 5,451,360.
Although vertical axis carousel-type machines of the noted type have enjoyed substantial commercial acceptance and success, innovation remains desirable. In particular, in vertical axis carousel-type machines, the mold forces and the weight of the rotating equipment are parallel to the vertical axis of rotation, creating a bending moment with respect to the axis of rotation and the bearings and shaft that support the carousel. Carousel-type machines also require a substantial amount of valuable floor space in a manufacturing facility. It is a general object of the present disclosure, in accordance with one aspect of the disclosure, to provide a method and apparatus for compression molding plastic articles, such as plastic closures and plastic liners within closure shells, which reduce the forces applied to the support frame and bearings, reduce maintenance requirements and the amount of energy needed to operate the machine, and/or reduce the amount of floor space required per machine.
The present disclosure involves a number of aspects that can be implemented separately from or in combination with each other.
A compression molding machine in accordance with a first aspect of the present disclosure includes a support mounted for rotation around an axis and a plurality of angularly spaced molds disposed around the support. Each of the molds includes a first mold segment and a second mold segment. At least one of the mold segments is movable with respect to the other mold segment between a closed position for compression molding a plastic article, and an open position for removing a molded article from the mold and placing a mold charge into the mold. An apparatus is provided for placing mold charges into the molds in sequence.
The apparatus for placing mold charges into compression molds in sequence, in accordance with a further aspect of the present disclosure, includes a plate for rotation around a first axis and at least one mold charge placement mechanism carried adjacent to a periphery of the plate. The mold charge placement mechanism includes a placement arm mounted for rotation around a second axis perpendicular to the first axis, and a cup on an end of the arm for placing mold charges into the compression molds as the molds pass in sequence adjacent to the periphery of the plate. In preferred embodiments in accordance with this aspect of the disclosure, the plate has a circular periphery, and there are a pair of mold charge placement mechanisms at diametrically opposed positions on the plate. A gear is coupled to driven shafts of the mold charge placement mechanisms for rotating the shafts and arms around axes perpendicular to the first axis and coaxial with each other. The gear may be stationary or may itself be rotated by a gear shaft independently of rotation of the plate. A cutter blade severs mold charges from an extruder nozzle or the like as the mechanisms are rotated on the plate. Vacuum and air under pressure preferably are applied selectively to the cups for retaining the mold charges in the cups as the mold charges are transported from the nozzle to the molds, and for assisting separation of the mold charges from the cups into the molds.
A machine for compression molding plastic articles, in accordance with another aspect of the disclosure, includes a first array of compression molds and a second array of compression molds mounted on a support for movement through respective first and second mold paths. Each mold includes mold segments, at least one of which is movable between a closed position and an open position for removing a molded article from the mold and placing a mold charge into the mold. A first mold charge placement apparatus is disposed adjacent to the first path for placing mold charges into molds of the first array in sequence. A second mold charge placement apparatus is disposed adjacent to the second path for placing mold charges into molds of the second array in sequence independently of the first apparatus. Operation of the first and second mold charge placement apparatuses preferably is synchronized to movement of the support. The support preferably includes a wheel mounted for rotation around a horizontal axis, with the first and second arrays of compression molds being disposed on axially opposed sides of the wheel.